Useful advice in an extremity (3)

I believe the answer is:

tip

I'm a little stuck... Click here to teach me more about this clue!

This clue could be a double definition.

'useful advice' is the first definition.
'tip' can be an answer for 'advice' (a tip is a piece of advice). I'm not certain of the 'useful' bit.

'an extremity' is the second definition.
(I know that tip is a type of end)

'in' is the link.

Can you help me to learn more?

(Other definitions for tip that I've seen before include "Pointed extremity" , "Point; sweetener" , "Dump; extremity" , "Point of gratuity" , "Small amount" .)

I've seen this clue in The Globe and Mail.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.